The present invention relates generally to multi-carrier communication systems and, more particularly, to management of uplink resources in a multi-carrier communication system.
Enhanced uplink, also known as High Speed Uplink Packet Access (HSUPA) was introduced in Release 6 of the Wideband Co-Division Multiple Access (WCDMA) standard to provide higher data rates on the uplink. HSUPA supports data rates of up to 11.52 megabits per second in the uplink using higher order modulation, fast power control, fast scheduling, and fast hybrid ARQ (HARQ) with soft combining. Two new physical uplink channels were added to the WCDMA standards to support HSUPA: the enhanced dedicated physical data channel (E-DPDCH) and the enhanced dedicated physical control channel (E-DPCCH). The E-DPDCH is the uplink channel used to carry user data bits from the mobile terminal to the base station, referred to in the standard as an enhanced NodeB (eNodeB). The E-DPCCH carries control information necessary to enable the base station to demodulate and decode the E-DPDCH.
Conventional WCDMA systems operate with a single uplink carrier. Release 8 of the WCDMA standard will allow transmission from the base station to the mobile terminals on two adjacent carriers. On the uplink, the mobile terminals will still use a single carrier for uplink transmissions. However, the mobile terminals may be allowed to switch between two different uplink carriers that are paired with the two downlink carriers.
Realizing the high data rates that are supported by HSUPA has been challenging. When a user terminal transmits at a high data rate on the uplink carrier, a high signal-to-interference plus noise ratio (SINR) at the receiver is needed in order to demodulate and decode the transmission. This means that the user terminals' receive power at the base station must be high, which will create interference for other users (e.g., voice users or low rate data users), as well as important control channels. These other users will then need to increase their transmit power to avoid degradation, thus further increasing the interference levels at the receiver. When the interference levels become too high, the system becomes unstable.
Therefore, improvements in managing uplink resources are needed in order to manage the interference generated by high data rate users.